The present invention relates generally to a method and an apparatus for recording an image of an original on a recording medium, and more particularly to such a method and an apparatus in which image data are recorded in a multiplexed or composite manner.
Heretofore, known in the art is a recording apparatus which uses a photosensitive and pressure-sensitive recording medium. Such a recording medium is classified into two types; one is of a self-contained type and another is of a transfer type. In he self-contained type recording medium, an encapsulated chromogenic material or dye precursor and a developer material are co-deposited on one surface of a single substrate as one layer or as two contiguous layers. In the transfer type recording medium, the developer material is coated on a separate substrate as a separate developer sheet. The self-contained type recording medium is disclosed in U.S. Pat. No. 4,440,846 and the transfer type recording medium is disclosed in U.S. Pat. No. 4,399,209.
More specifically the photosensitive and pressure-sensitive recording medium has the substrate on which three kinds of pressure rupturable microcapsules are dispersely deposited. Cyan (C), magenta (M) and yellow (Y) chromogenic materials or dye precursors are separately encapsulated in the microcapsules together with a photo-curing or photo-softening material. The three kinds of the microcapsules are different in photo-sensitivity depending upon the wavelength of light. For example, the microcapsules containing cyan, magenta, and yellow chromogenic materials are photo-cured or photo-softened in response to the wavelengths of 650 nm, 550 nm, 450 nm, respectively. By exposing the lights of such wavelengths onto the recording medium in accordance with the image cf the original, a latent image corresponding to the original image is formed thereon. The recording medium is then subjected to pressure development to rupture the microcapsules which have not photo-cured or have remained softened and to react the chromogenic materials flown out from the ruptured microcapsules with the developer material, whereby a visible image is provided on the same recording medium or the separate developer sheet.
In a prior art recording apparatus using such recording medium, an image of a color original is scanned by a white light and the light reflected on the surface of the original is successively passed through color resolution filters of red, green and blue, and in response to an output from each of the filters three mask members are produced. Through the respective mask members, the recording medium is exposed in multiplexed manner. This type of recording apparatus is advantageous in that energy required for exposing the recording mediums is greatly reduced in comparison wi&h an apparatus of the type in which a white light is irradiated onto the color original and the reflected light is directly exposed on the recording medium.
In a copending U.S. patent application Ser. No. 050,313 filed May 14, 1987 by Sangyouji et al, it has been proposed an apparatus in which a mask member is produced utilizing an electrophotographying process. Such an apparatus will be briefly described with reference to FIG. 1.
In FIG. 1, with a laser exposure unit 1 and a xerography unit 2, a monochromatic (preferably black) toner image corresponding to each of the resolution colors of the original color image, i.e. red, green and black, is separately formed on a light transmissive member 3 (hereinafter referred to as "red mask member", "green mask member", and "blue mask member", respectively). Such a light transmissive member 3 is moved toWard the direction indicated by an arrow A. The red, green and blue mask members are successively set to a predetermined position above the recording sheet S and brought to be in facial contact with the recording sheet S. Each time the mask member is set, the recording sheet S is exposed by a light which has passed through the corresponding filter 4. The recording sheet S is thus exposed in multiplexed manner. As shown in FIG. 2, the recording sheet S is next fed into a nip between a pair of pressing rollers 6 with which the uncured microcapsules are ruptured and the chromogenic material which flows out from the microcapsules reacts with the developer material to thereby form a visible image.
Referring next to FIGS. 3A through 3E, the relation of the color hues betWeen the mask members and the recording sheet S will be described. The red mask member 3R is formed in accordance with a picture signal obtained by scanning a white light on the color picture original and then passing the reflected light through a red-color transmitting filter. As shown in FIG. 3A, a toner which is a light shielding material is adhered to areas designated by numerals 2, 4 and 5 by means of an electrophotography laser printer or the like. A light having a wavelength of 650 nm is irradiated through the red mask member onto the recording medium and the exposed microcapsules encapsulating the cyan chromogenic material (which microcapsules will hereinafter be referred to as "cyan microcapsules") on the recording medium are photo-cured. That is, the cyan microcapsules in areas of 1 and 3 on the recording sheet S are photo-cured and the remaining microcapsules remain uncured.
Next, as shown in FIG. 3B, a light having a wavelength of 550 nm is irradiated which selectively cures the microcapsules encapsulating the magenta chromogenic material (which microcapsules will hereinafter be referred to as "magenta microcapsules") That is, the magenta microcapsules in the areas of 1, 2 and 5 are cured. Likewise, upon irradiating on the recording sheet S a light having a wavelength of 450 nm which selectively photo-cures the microcapsules encapsulating yellow chromogenic material (which microcapsules will hereinafter be referred to as "yellow microcapsules"), the yellow microcapsules in the areas of 1 and 2 are photo-cured.
The recording sheet S which has thus been multiplexedly exposed is pressed by the pair of pressure rollers 6 to rupture the uncured microcapsules. Upon reaction of the chromogenic material which flows out from the ruptured microcapsules with the developer material, the color latent image is developed and a visible color image appears as shown in FIG. 3E. Specifically, in the area 2 of the recording sheet S, since only the cyan microcapsules remain uncured, the cyan-color appears when developed. Since the magenta and yellow microcapsules remain uncured in the area of 3, the red color appears when developed. Since all kinds of microcapsules remain uncured in the area of 4, black-color appears when developed. Similarly, green-color appears in the area 5 and white-color appears in the area 1.
It is to be noted that the wavelengths of the light which photo-cure the respective microcapsules need not be in coincidence with those of three primary colors of red, green and blue. The wavelengths of the photo-curing lights can be selected, provided that they are sensitive to the respective microcapsules and no cross talk is caused.
In the recording apparatus as described above, a photo-slide may be utilized in place of the mask member. By using the photo-slide, a post card or such kind of printed matters can be produced. Printed matters can also be produced based on photographs, in which case the light reflected from the photograph is used.
In the prior art recording apparatus, it has been impossible to produce the printed matters while modifying the images of the photo slide or pictures with modification.
Further, in the case where the image on the original is made up of a chromatic picture image and a monochromatic (for example, black) fine line image (for example, alpha/numerics or characters), the respective colors of the reproduced image are displaced from one another if the respective color mask members are not accurately placed in a predetermined position when exposed. Particularly, in the case where black fine lines are included in the original, the displacement of the colors tends to be notable, since the black color is reproduced by an additive mixture of cyan, magenta and yellow colors.
When high resolution mask members are prepared for reproducing small-size characters of, for example, several points, the resolution of the reproduced character is lowered if there is a displacement in positioning the color mask members. Consequently, the reproduced character image becomes low in quality.
As to the picture image which is required to be reproduced in half-tone images, a quasi-gradation technique, such as an area gradation method is generally employed when preparing the mask members. For example, 8.times.8 dot matrix undertakes reproduction of a 64-gradation half-tone image. In such a case, provided that the printer resolution is 10 dot/mm, the size of one dot is 100 micrometer. Accordingly, one side of the pixel defined by 8.times.8 dot matrix is 800 micrometer (0.8 mm). If the line images are reproduced with 2-gradation, it is impossible to reproduce lines interspaced with less than 0.8 mm, and thus the solution of such line image is extremely lowered. In order to provide a good reproducibility of the line images while maintaining a good reproducibility of the picture images, a quasi-gradation technique, such as an edge gradation method or an average error square method, is employed when the mask member is prepared. However, a complicated arithmetic processing needs to be carried out for expressing the original image in a quasi-gradation, so that a software program and a hardware, such as a CPU, becomes large in scale, and in addition, a memory of a large storage capacity needs to be mounted. Moreover, it takes a long period of time for carrying out the arithmetic operation, and hence the recording speed is lowered.